Method of forming particle layer on substrate, method of planarizing irregular surface of substrate and particle-layer-formed substrate

ABSTRACT

The present invention provides a method of forming on a substrate a particle layer highly adherent to the substrate, which comprises the steps of spreading a dispersion (I) comprising a dispersing medium and, dispersed therein, solid particles being surface treated with a compound acting as a binder on a liquid (II) having a specific gravity higher than that of the dispersing medium, said liquid (II) being immiscible with the dispersing medium, subsequently removing the dispersing medium from the dispersion (I) to thereby arrange the solid particles on the liquid (II) so that a particle layer is formed on the liquid (II) and thereafter transferring the particle layer onto a substrate. Moreover, the present invention provides a method of planarizing an irregular surface of a substrate, which comprises transferring the above particle layer to an irregular surface of a substrate and removing parts of the particle layer formed on protrudent parts of the substrate to thereby planarize the irregular surface of the substrate and also provides a particle-layer-formed substrate comprising a substrate and, superimposed on a surface thereof, the particle layer obtained by each of the above methods.

TECHNICAL FIELD

The present invention relates to a method of forming a particle layer ona substrate, a method of planarizing (flattening) an irregular surfaceof a substrate and a particle-layer-formed substrate. More particularly,the present invention is concerned with a method of forming on asubstrate a particle layer highly adherent to the substrate, a method ofplanarizing an irregular surface of a substrate in which a particlelayer is provided in recessed parts of the irregular surface of thesubstrate and a particle-layer-formed substrate having excellentadherence between the particle layer and the substrate.

BACKGROUND ART

The Langmuir-Blodgett's technique is known as a method of forming amonomolecular film on a substrate.

In this technique, the monomolecular film is formed on the substrate byspreading a monomolecular film on a gas-liquid interface andtransferring the monomolecular film onto a substrate. A compound havinga surface activity, for example, a compound having hydrophilic andhydrophobic groups in its molecule is used as a compound for forming themonomolecular film.

On the other hand, the following methods are generally known for formingon a substrate a particle layer from solid particles having no surfaceactivity.

(1) The one method comprises spreading on a substrate a dispersioncomprising a dispersing medium and, dispersed therein, solid particles,for example, a spherical-polystyrene suspension (latex) and thereafterevaporating the dispersing medium to thereby form a two-dimensionalcrystal layer, for example, a monoparticulate layer (Hyomen (surface),Vol. 31, No. 5, pp. 11-18 (1993)).

(2) The other method comprises contacting a dispersion comprising adispersing medium and, dispersed therein, solid particles with a liquidimmiscible with the dispersing medium to thereby cause the liquid-liquidinterface to adsorb the solid particles of the dispersion so that amonoparticulate layer is formed at the interface and thereaftertransferring the monoparticulate layer onto a substrate to thereby formthe monoparticulate layer on the substrate (Japanese Patent Laid-openPublication No. 2(1990)-307571).

However, the formation of the particle layer on the substrate accordingto the above methods encounters problems such that the resultantparticle layer is inferior in adhesion to the substrate.

With respect to semiconductor devices or electronic devices havingmultilevel interconnection structures, an irregular surface (step) onthe substrate is formed during the respective manufacturing processes,so that occasionally the planarizing of the step is required.

For example, each layer of a semiconductor device having multilevelinterconnection structure has a step between wiring and nonwiring partsthereof, so that the step must be eliminated to thereby attainplanarizing prior to formation of an upper wiring layer. Further, withrespect to a color-filter-formed transparent electrode plate of a liquidcrystal color display device, the step of the color filter must beeliminated, to thereby attain planarizing during the process ofmanufacturing the same. Still further, with respect to a TFT-formedtransparent electrode plate for use in liquid crystal displays and thelike, it is needed to eliminate the step of the TFT formed thereon tothereby attain planarizing during the process of manufacturing the same.

The present invention has been made in the above circumstances. Thus,objects of the present invention are to provide a method of forming on asubstrate a particle layer highly adherent to the substrate, a method ofplanarizing an irregular surface of a substrate and aparticle-layer-formed substrate having a highly adherent particle layerformed on a substrate.

DISCLOSURE OF THE INVENTION

The method of forming a particle layer on a substrate according to thepresent invention comprises the steps of spreading a dispersion (I)comprising a dispersing medium and, dispersed therein, solid particlesbeing surface treated with a compound acting as a binder on a liquid(II) having a specific gravity higher than that of the dispersingmedium, said liquid (II) being immiscible with the dispersing medium,subsequently removing the dispersing medium from the dispersion (I) tothereby arrange the solid particles on the liquid (II) so that aparticle layer is formed on the liquid (II) and thereafter transferringthe particle layer onto a substrate.

The method of planarizing an irregular surface of a substrate accordingto the present invention comprises the steps of spreading a dispersion(I) comprising a dispersing medium and, dispersed therein, solidparticles being surface treated with a compound acting as a binder on aliquid (II) having a specific gravity higher than that of the dispersingmedium, said liquid (II) being immiscible with the dispersing medium,subsequently removing the dispersing medium from the dispersion (I) tothereby arrange the solid particles on the liquid (II) so that aparticle layer is formed on the liquid (II), then transferring theparticle layer onto an irregular surface of a substrate and thereafterremoving parts of the particle layer formed on protrudent parts of thesubstrate to thereby cause the particle layer to remain at recessedparts of the substrate.

The particle-layer-formed substrate of the present invention comprises asubstrate and, superimposed on a surface thereof, the particle layerobtained by each of the above methods.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 (a), 1(b) and 1(c) are views for explaining the particle layerforming method of the present invention, and FIG. 2 is an electronmicrograph showing the particulate structure of the monoparticulatelayer part of the particle-layer-formed glass plate.

I: dispersion (I), II: liquid (II), 1: dispersing medium, 2: solidparticles 3: particle layer, 4: binder, 5: substrate

BEST MODE FOR CARRYING OUT THE INVENTION

Method of Forming Particle Layer

First, the particle layer forming method of the present invention willbe illustrated below.

The method of forming a particle layer on a substrate according to thepresent invention comprises the steps of spreading a dispersion (I)comprising a dispersing medium and, dispersed therein, solid particlesbeing surface treated with a compound acting as a binder on a liquid(II) having a specific gravity higher than that of the dispersingmedium, said liquid (II) being immiscible with the dispersing medium,subsequently removing the dispersing medium from the dispersion (I) tothereby arrange the solid particles on the liquid (II) so that aparticle layer is formed on the liquid (II) and thereafter transferringthe particle layer onto a substrate.

Particles of an inorganic compound such as SiO₂, TiO₂, ZrO₂ or SiC orparticles of a synthetic resin such as polystyrene are used as solidparticles in the formation of the above dispersion (I).

The particle size of the above particles is preferred to range fromabout 100 Å to about 100 μm though depending on the purpose of theformation of the particle layer on the substrate and the use of thesubstrate having the particle layer formed thereon.

The solid particles are used in varied form, for example, spherical,rod-shaped or fibrous form, depending on the purpose of the formation ofthe particle layer on the substrate and the use of the substrate havingthe particle layer formed thereon. In particular, when forming theparticle layer on the substrate according to the method of the presentinvention with the use of the dispersion (I) comprising the dispersingmedium and, dispersed therein, spherical particles having uniformparticle size as the solid particles, a uniform monoparticulate layer ofregularly arranged solid particles can be obtained on the substrate.

In the present invention, the dispersion (I) is prepared by surfacetreating the above solid particles with a compound acting as a binderand thereafter dispersing them in the dispersing medium.

Example of compound acting as a binder include a film forming componentof a film forming coating solution, for instance, an organosiliconcompound represented by the formula:

    R.sub.n Si(OR').sub.4-n

wherein R and R' may be identical with or different from each other andeach thereof represents a hydrogen atom, an alkyl group having 1 to 8carbon atoms, an aryl group or a vinyl group, and n is an integer of 0to 3.

Examples of the above organosilicon compounds includetetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane,tetraoctylsilane, methyltrimethoxysilane, methyltriethoxysilane,ethyltriethoxysilane, methyltriisopropoxysilane,dimethyldimethoxysilane, methyltributoxysilane, octyltriethoxysilane,phenyltrimethoxysilane, vinyltrimethoxysilane, diethoxysilane andtriethoxysilane.

In the present invention, any of β-diketone compounds such asdibutoxybisacetylacetonatozirconium,tributoxymonoacetylacetonatozirconium anddibutoxybisacetylacetonatotitanium and metal carboxylate such as tinoctylate, aluminum octylate and tin laurylate can also be used as thecompound acting as a binder.

Further, in the present invention, polysilazane is used as the compoundacting as a binder, which is preferred from the viewpoint of its highreactivity with the solid particles.

The surface treatment of the solid particles with the above compoundacting as a binder is conducted by, for example, the method selectedfrom among:

(a) method in which the solid particles are dispersed in an appropriatedispersing medium, for example, an organic solvent such as an alcohol,the above compound acting as a binder is added to the resultantdispersion and reaction of the compound acting as a binder is carriedout at temperatures not higher than the boiling point of the dispersingmedium;

(b) method in which the solid particles are dispersed in a dispersingmedium containing the compound acting as a binder; and

(c) method in which, when the solid particle dispersion is a colloidalparticle dispersion such as silica sol, the colloidal particledispersion is charged directly (or according to necessity aftersubstitution of the dispersing medium for an organic solvent) with thecompound acting as a binder.

In the above surface treatment, the compound acting as a binder ispreferably employed in an amount of 0.01 to 0.5 part by weight in termsof binder per part by weight of the solid particles. When the amount ofthe compound acting as a binder is less than 0.01 part by weight,occasionally the solid particles of the dispersion (I) mutuallyaggregate or precipitate in the liquid (II) at the time of spreading thedispersion (I) on the liquid (II). On the other hand, when the amountexceeds 0.5 part by weight, it is likely that a film is formed by excessbinder, so that the formation of the particle layer is prevented.

In the present invention, the dispersion obtained in the surfacetreatment of the solid particles with the compound acting as a binderaccording to any of the above methods can be used as the dispersion (I).However, it is preferred that the dispersing medium of the abovedispersion be substituted for an organic solvent such as a ketone, anether or an aromatic solvent prior to use as the dispersion (I) from theviewpoint of the dispersibility of the solid particles and thevolatility and evaporation of the dispersing medium after the spread ofthe dispersion (I) on the liquid (II).

Examples of the above organic solvents suitable for substituting thedispersing medium include methyl ethyl ketone, methyl isobutyl ketone,cyclohexane, dimethyl ether, diethyl ether, hexane, octane, toluene andxylene.

The concentration of solid particles in the dispersion (I) is preferredto range from 5 to 40% by weight. When this concentration is less than5% by weight, the time required for removing the dispersing medium fromthe dispersion (I) spread on the liquid (II) might be prolonged. On theother hand, when the concentration exceeds 40% by weight, occasionallyit is difficult to smoothly spread the dispersion (I) on the liquid (II)or the number of particles of the particle layer in the direction of thethickness thereof is locally varied the multiple particle layer isformed.

The liquid (II) used in the present invention has a specific gravityhigher than that of the dispersing medium of the above dispersion (I)and being immiscible with the dispersing medium.

This liquid (II) is not particularly limited as long as it has aspecific gravity higher than that of the above dispersing medium and isimmiscible with the dispersing medium. However, water is preferred fromthe viewpoint that its handling is easy.

In the present invention, the particle layer is formed on the substratethrough the following process.

i) The dispersion (I) is spread on the liquid (II) as shown in FIG. 1(a) by, for example, the method in which the dispersion (I) is gentlydropped on the liquid (II).

ii) The dispersing medium 1 of the dispersion (I) is removed by themethod in which the interface between the dispersion (I) and the liquid(II) is not disordered. For example, the method of evaporating thedispersing medium 1 from the dispersion (I) at atmospheric or reducedpressure is employed for removing the dispersing medium 1. This removalof the dispersing medium 1 from the dispersion (I) on the liquid (II)causes the solid particles 2 to arrange on the liquid (II) during theperiod from the start of the removal of the dispersing medium 1 to thecompletion of the removal of the dispersing medium 1, so that theparticle layer 3 is formed as shown in FIG. 1 (b).

iii) This particle layer on the liquid (II) is transferred onto asubstrate to thereby form the particle layer 3 on the substrate 5 asshown in FIG. 1 (c).

The method of transferring the particle layer onto the substrate is notparticularly limited as long as it does not damage the particle layer.For example, preferred is a method in which the substrate is previouslysunk in the liquid bath containing the liquid (II) and lifted after thecompletion of the above step (ii) or another in which the substrate ispreviously sunk in the liquid bath containing the liquid (II) and theliquid (II) is gradually withdrawn from the liquid bath after thecompletion of the above step (ii).

iv) The substrate having the particle layer formed thereon is dried andaccording to necessity further heated, so that the solid particlesconstituting the particle layer adhere to each other by means of thebinder and that further the binder bonds with the substrate to therebyrealize excellent adherence between the particle layer and thesubstrate.

Method of Planarizing Irregular Surface of Substrate

Next, the method of planarizing an irregular surface of a substrateaccording to the present invention will be described in detail.

The method of planarizing an irregular surface of a substrate accordingto the present invention comprises forming a particle layer on anirregular surface of a substrate in the same manner as described aboveand thereafter removing parts of the particle layer formed on protrudentparts of the substrate to thereby planarize the irregular surface of thesubstrate.

The removal of the particle layer formed on protrudent parts of thesubstrate is carried out by, for example, polishing.

The above formation of a particle layer on an irregular surface of asubstrate followed by removal of the particle layer formed on protrudentparts of the substrate causes the particle layer to remain embedded inand bonded by a binder to only recessed parts of the substrate, therebyplanarizing the irregular surface of the substrate.

Particle-layer-formed Substrate

The particle-layer-formed substrate of the present invention comprises asubstrate and, formed on its surface, the particle layer obtainedaccording to the above method.

In the present invention, any type of substrate can be employed as longas the particle layer can be formed on its surface according to theabove method. In particular, examples of the particle-layer-formedsubstrates of the present invention include:

a high-density optical or magnetic disk having a particle layer formedthereon made from, for example, silica according to the above method;

a CCD (charge coupled device) having a microlens made of a particlelayer formed from, for example, titanium oxide according to the abovemethod;

a face-plate of display such as a CRT or a liquid crystal display unithaving on its surface a particle layer formed from, for example, silicaaccording to the above method;

a semiconductor device having a multilevel interconnection structureobtained by forming an insulating particle layer of, for example, silicaon nonwiring parts of each level according to the above method tothereby planarizing the step between wiring parts and nonwiring parts;

a color-filter-formed transparent electrode plate for use in a colorliquid crystal display device, obtained by forming an insulatingparticle layer of, for example, silica on a substrate surface having acolor filter so as to planarize the step of the color filter areaaccording to the above method; and

a TFT (thin film transistor)-formed transparent electrode plate for usein a liquid crystal display device, obtained by forming an insulatingparticle layer of, for example, silica on a substrate surface having aprotrudent TFT so as to planarize the step of the TFT area according tothe above method.

All the above particle-layer-formed substrates of the present inventionare excellent in the adherence between the particle layer and thesubstrate.

The high-density optical or magnetic disk having the above particlelayer at its surface is excellent in texturing characteristics. Theface-plate of display having the above particle layer at its surface isexcellent in antireflection performance.

EFFECT OF THE INVENTION

The present invention provides the particle-layer-formed substratehaving a highly adherent particle layer and enables forming amonoparticulate layer in which solid particles are regularly arranged ona substrate.

Further, the present invention enables forming the particle layer fromany of various types of solid particles and thus enables obtaining aparticle-layer-formed substrate having a high light transmission, a lowhaze and an excellent antireflection performance by forming a layer ofsuitable solid particles such as those of silica, titania or alumina ona substrate.

Still further, the present invention enables embedding the particlelayer only in recessed parts of the substrate having irregular surface,so that the irregular surface of the substrate can be planarized.

EXAMPLE

The present invention will be described below with reference to thefollowing Examples, which in no way limit the scope of the invention.

Example 1

20 g of polysilazane (PHPS (trade name) produced by Tonen Corp.,concentration: 10 wt. %, solvent: xylene) was added to 100 g ofcommercially available organosilica sol (Oscal (trade name) produced byCatalysts & Chemicals Industries Co., Ltd., average particle size: 300nm, concentration: 10 wt. %, solvent: ethanol) and heated at 50° C. for5 hr to thereby surface treat the silica particles. Then, the solvent ofthe resultant dispersion was substituted for MIBK, thereby obtaining a20% by weight silica particle dispersion. A lifting apparatus togetherwith a glass plate mounted thereon was sunk in the water of a watervessel. 1 g of the above 20% by weight silica particle dispersion wasdropped on the surface of the water and left undisturbed for 2 min.During this period, MIBK evaporated off, so that a monoparticulate layerof silica was formed on the surface of the water. Thereafter, the glassplate was gently lifted by the lifting apparatus, thereby transferringthe monoparticulate layer of silica onto the glass plate. The resultantparticle-layer-formed glass plate was heated at 300° C. for 30 min.

This particle-layer-formed glass plate was evaluated with respect to themonolayer formation in the particle layer, the adherence between theparticle layer and the plate and the light transmission, the lightreflectance and the haze of the particle-layer-formed glass plate in thefollowing manners. An electron micrograph (15,000 magnification) of themonoparticulate layer part of the particle-layer-formed glass plate isshown in FIG. 2.

Monolayer formation in particle layer

The silica particle layer was observed by means of a scanning electronmicroscope and an optical microscope to find whether it is composed of amonolayer or multilayer. It was judged as being good when the proportionof multilayer parts is low.

Adherence of particle layer to plate

The tape peeling test was conducted and the condition of peeling of thesilica particle layer was visually inspected.

Light transmission through particle-layer-formed glass plate

The light transmission at 550 nm was measured by the use of hazecomputer manufactured by Suga Test Instruments Co., Ltd.

Light reflection on particle-layer-formed glass plate

The light reflectance at 550 nm was measured by the use ofspectrophotometer manufactured by Hitachi, Ltd.

Haze of particle-layer-formed glass plate

The diffused light transmission and parallel light transmission at 550nm were measured by the use of haze computer manufactured by Suga TestInstruments Co., Ltd., and the haze was calculated by the formula:

    Haze=(diffused light transmission/parallel light transmission)×100.

The results are shown in Table 1.

Example 2

A particle-layer-formed glass plate was produced in the same manner asin Example 1 except that 20 g of tetraethoxysilane (Ethyl silicate 28(trade name) produced by Tama Chemicals Co., Ltd., concentration: 10 wt.%, solvent: ethanol) and 1 g of 30% by weight aqueous ammonia as ahydrolysis catalyst were added to 100 g of commercially availableorganosilica sol (Oscal (trade name) produced by Catalysts & ChemicalsIndustries Co., Ltd., average particle size: 300 nm, concentration: 10wt. %, solvent: ethanol) and heated at 50° C. for 10 hr to therebysurface treat the silica particles and then the solvent of the resultantdispersion was substituted for MIBK, thereby obtaining a 20% by weightsilica particle dispersion. This particle-layer-formed glass plate wasevaluated with respect to the monolayer formation in the particle layer,the adherence between the particle layer and the plate and the lighttransmission, the light reflectance and the haze of theparticle-layer-formed glass plate.

The results are shown in Table 1.

Example 3

A particle-layer-formed glass plate was produced in the same manner asin Example 1 except that 20 g of dibutoxybisacetylacetonatotitanium(TC-100 (trade name) available from Matsumoto Trading Co., Ltd.,concentration: 10 wt. %, solvent: ethanol) was added to 100 g ofcommercially available organosilica sol (Oscal (trade name) produced byCatalysts & Chemicals Industries Co., Ltd., average particle size: 300nm, concentration: 10 wt. %, solvent: ethanol) and heated at 50° C. for1 hr to thereby surface treat the silica particles and then the solventof the resultant dispersion was substituted for MIBK, thereby obtaininga 20% by weight silica particle dispersion. This particle-layer-formedglass plate was evaluated with respect to the monolayer formation in theparticle layer, the adherence between the particle layer and the plateand the light transmission, the light reflectance and the haze of theparticle-layer-formed glass plate.

The results are shown in Table 1.

Example 4

A particle-layer-formed glass plate was produced in the same manner asin Example 1 except that 20 g of dibutoxybisacetylacetonatotitanium(TC-100 (trade name) available from Matsumoto Trading Co., Ltd.,concentration: 10 wt. %, solvent: ethanol) was added to 100 g ofcommercially available titania sol (Neosunveil (trade name) produced byCatalysts & Chemicals Industries Co., Ltd., average particle size: 15nm, concentration: 10 wt. %, solvent: ethanol) and heated at 50° C. for1 hr to thereby surface treat the titania particles and then the solventof the resultant dispersion was substituted for MIBK, thereby obtaininga 20% by weight titania particle dispersion. This particle-layer-formedglass plate was evaluated with respect to the monolayer formation in theparticle layer, the adherence between the particle layer and the plateand the light transmission, the light reflectance and the haze of theparticle-layer-formed glass plate.

The results are shown in Table 1.

Example 5

A particle-layer-formed glass plate was produced in the same manner asin Example 1 except that 20 g of aluminum stearate (concentration: 10wt. %, solvent: ethanol) was added to 100 g of commercially availablealumina sol (Cataloid-AS (trade name) produced by Catalysts & ChemicalsIndustries Co., Ltd., average particle size: 10×100 Å, concentration: 10wt. %, solvent: ethanol) and heated at 50° C. for 1 hr to therebysurface treat the alumina particles and then the solvent of theresultant dispersion was substituted for MIBK, thereby obtaining a 10%by weight alumina particle dispersion. This particle-layer-formed glassplate was evaluated with respect to the monolayer formation in theparticle layer, the adherence between the particle layer and the plateand the light transmission, the light reflectance and the haze of theparticle-layer-formed glass plate.

The results are shown in Table 1.

Example 6

A particle-layer-formed glass plate was produced in the same manner asin Example 1 except that 20 g of polysilazane (PHPS (trade name)produced by Tonen Corp, concentration: 10 wt. %, solvent: xylene) wasadded to 100 g of commercially available latex dispersion (Microgel(trade name) produced by NIPPON PAINT CO., LTD., average particle size:300 nm, concentration: 10 wt. %, solvent: ethanol) and heated at 50° C.for 5 hr to thereby surface treat the latex particles and then thesolvent of the resultant dispersion was substituted for MIBK, therebyobtaining a 10% by weight latex particle dispersion. Thisparticle-layer-formed glass plate was evaluated with respect to themonolayer formation in the particle layer, the adherence between theparticle layer and the plate and the light transmission, the lightreflectance and the haze of the particle-layer-formed glass plate.

The results are shown in Table 1.

Comparative Example 1

A particle-layer-formed glass plate was produced in the same manner asin Example 1 except that the solvent of commercially availableorganosilica sol (Oscal (trade name) produced by Catalysts & ChemicalsIndustries Co., Ltd., average particle size: 300 nm, concentration: 10wt. %, solvent: ethanol) was substituted for MIBK, thereby obtaining a20% by weight silica particle dispersion. This particle-layer-formedglass plate was evaluated with respect to the monolayer formation in theparticle layer, the adherence between the particle layer and the plateand the light transmission, the light reflectance and the haze of theparticle-layer-formed glass plate.

The results are shown in Table 1.

Comparative Example 2

A particle-layer-formed glass plate was produced in the same manner asin Example 1 except that the solvent of commercially available latexdispersion (Microgel (trade name) produced by NIPPON PAINT CO., LTD.,average particle size: 300 nm, concentration: 10 wt. %, solvent:ethanol) was substituted for MIBK, thereby obtaining a 20% by weightlatex particle dispersion. This particle-layer-formed glass plate wasevaluated with respect to the monolayer formation in the particle layer,the adherence between the particle layer and the plate and the lighttransmission, the light reflectance and the haze of theparticle-layer-formed glass plate.

The results are shown in Table 1.

                  TABLE 1                                                         ______________________________________                                                        Particle-layer-formed                                                         glass plate                                                   Particle layer    Light     Reflect-                                                      Adherence transmission                                                                            ance   Haze                                   Monolayer   to plate  (%)       (%)    (%)                                    ______________________________________                                        Ex. 1 Good      Good      95      0.8    0.9                                  Ex. 2 Good      Good      94      0.9    1.0                                  Ex. 3 Good      Good      95      0.9    0.9                                  Ex. 4 Good      Good      90      7.5    0.3                                  Ex. 5 Good      Good      92      4.8    0.0                                  Ex. 6 Good      Good      92      5.3    1.4                                  Comp  Poor      Poor      93      1.5    1.4                                  Ex. 1                                                                         Comp  Good      Poor      90      5.5    1.9                                  Ex. 2                                                                         ______________________________________                                    

It is apparent from Table 1 that the particle-layer-formed substrate ofthe present invention is excellent in the adherence between the particlelayer and the substrate and that the particle layer is in the state of auniform monolayer in which the particles are regularly arranged.

Further, it is apparent that the particle-layer-formed substrate of thepresent invention exhibits high optical performance and is suitable foruse as a high-density recording optical or magnetic disc, a CCD, anoptical device or a face-plate of display of CRT or liquid crystaldisplay device.

Example 7

20 g of polysilazane (PHPS (trade name) produced by Tonen Corp.,concentration: 10 wt. %, solvent: xylene) was added to 100 g ofcommercially available organosilica sol (Oscal (trade name) produced byCatalysts & Chemicals Industries Co., Ltd., average particle size: 300nm, concentration: 10 wt. %, solvent: ethanol) and heated at 50° C. for5 hr to thereby surface treat the silica particles. Then, the solvent ofthe resultant dispersion was substituted for MIBK, thereby obtaining a20% by weight silica particle dispersion. Using as a substrate asemiconductor model device in which a wiring step height of 0.6 μm wasformed, a semiconductor device carrying a monoparticulate layer ofsilica was prepared through a step of heating at 300° C. for 30 min inthe same manner as in Example 1.

This particle-layer-formed semiconductor device was set on a polishingapparatus, by which the silica particles on the wiring were selectivelypolished away, followed by formation of an interlayer insulating film ofsilica and an upper-layer wiring.

A section of the thus formed multilevel interconnection structure wasobserved by a scanning electron microscope and it was found that theabove interlayer insulating film of silica had excellent planarization.

We claim:
 1. A method of forming a particle layer on a substrate, which comprises the steps of spreading a dispersion (I) comprising a dispersing medium and, dispersed therein, solid particles, the surface of said particles including a compound acting as a binder on a liquid (II) having a specific gravity higher than that of the dispersion medium, said liquid (II) being immiscible with the dispersing medium, subsequently removing the dispersing medium from the dispersion (I) to thereby arrange the solid particles on the liquid (II) so that a particle layer is formed on the liquid (II) and thereafter transferring the particle layer onto a substrate.
 2. A particle-layer-formed substrate comprising a substrate and, superimposed on a surface thereof, the particle layer obtained by the method as claimed in claim
 1. 3. A particle-layer-formed substrate as claimed in claim 2, wherein the substrate is dried and heat-treated after the particle layer is transferred.
 4. A method of forming a particle layer on a substrate as claimed in claim 1, which further comprises, after transferring the particle layer onto the substrate, the step of drying and heat-treating the substrate.
 5. A method of planarizing an irregular surface of a substrate, which comprises the steps of spreading a dispersion (I) comprising a dispersing medium and, dispersed therein, solid particles, the surface of said solid particles including a compound acting as a binder on a liquid (II) having a specific gravity higher than that of the dispersing medium, said liquid (II) being immiscible with the dispersing medium, subsequently removing the dispersing medium from the dispersion (I) to thereby arrange the solid particles on the liquid (II), then transferring the particle layer onto an irregular surface of a substrate having protrudent and recessed parts and thereafter removing parts of the particle layer formed on the protrudent parts of the substrate to planarize the irregular surface of the substrate.
 6. A particle-layer-formed substrate comprising a substrate and, superimposed on a surface thereof, the particle layer obtained by the method as claimed in claim
 5. 7. A particle-layer-formed substrate as claimed in claim 6, wherein the substrate is dried and heat-treated after the particle layer is transferred, and before the particle layer is removed from the protrudent parts.
 8. A method of forming a particle layer on a substrate as claimed in claim 5, which further comprises, after transferring the particle layer onto the irregular surface of the substrate and before the particle layer is removed from the protrudent parts, the step of drying and heat-treating the substrate. 